Cyclopropyl (Trimethylsilyl) Acetylene: FAQs & Lab Guide

Cyclopropyl (trimethylsilyl) acetylene is a versatile organosilicon alkyne building block widely used in organic synthesis as a protected terminal alkyne and cyclopropyl-group donor.

Chemical Name

Cyclopropyl (trimethylsilyl) acetylene

Synonyms

(Cyclopropylethynyl)trimethylsilane; TMS-cyclopropylacetylene

Molecular Formula

C8H14Si

Molecular Weight

138.28 g/mol

CAS Number

68922-46-3

Key Functional Groups

Internal alkyne (C≡C), trimethylsilyl (TMS) group, cyclopropyl ring

Aladdin SKU

C684376

What Is Cyclopropyl (Trimethylsilyl) Acetylene?

Cyclopropyl (trimethylsilyl) acetylene (CAS 68922-46-3, MW 138.28 g/mol, formula C₈H₁₄Si) is an organosilicon compound featuring a trimethylsilyl (TMS) group and a cyclopropyl moiety connected through an acetylenic (C≡C) linkage. The TMS group serves as a protecting group for the terminal alkyne, allowing selective deprotection under mild fluoride or base conditions to liberate the reactive cyclopropylacetylene. This dual functionality—an easily removable silyl group and a strained cyclopropyl ring—makes it a valuable reagent and building block in modern organic synthesis, medicinal chemistry, and materials science research.

Physical and Chemical Properties

Cyclopropyl (trimethylsilyl) acetylene is typically a colorless to pale yellow liquid at room temperature. Its key physicochemical characteristics include:

• Molecular Formula: C₈H₁₄Si
• Molecular Weight: 138.28 g/mol
• CAS Number: 68922-46-3
• Functional Groups: TMS-protected alkyne, cyclopropyl ring

The trimethylsilyl group increases the stability of the alkyne toward polymerization and undesired side reactions, while the cyclopropyl ring introduces ring strain that can be exploited in ring-opening and cycloaddition chemistries. The compound is moderately lipophilic and should be handled under inert atmosphere conditions to prevent moisture-induced degradation of the Si–C bond.

Synthetic Applications and Reactivity

Cyclopropyl (trimethylsilyl) acetylene serves multiple roles in synthetic chemistry:

1. TMS-Deprotection to Terminal Alkyne: Treatment with fluoride sources (e.g., TBAF, KF) or mild base (e.g., K₂CO₃ in MeOH) cleanly removes the TMS group, generating cyclopropylacetylene in situ for use in Sonogashira couplings, click chemistry (CuAAC), and other alkyne-based transformations.
2. Sonogashira Coupling: The compound or its deprotected counterpart undergoes palladium/copper-catalyzed cross-coupling with aryl and vinyl halides to introduce the cyclopropyl-alkyne motif into complex molecules, which is particularly relevant in medicinal chemistry for drug candidate synthesis.
3. Cycloaddition Reactions: The strained cyclopropyl ring participates in [2+2] and other cycloaddition reactions, offering routes to polycyclic scaffolds.
4. Nucleophilic Addition: After desilylation and metalation (e.g., with n-BuLi), the resulting lithio-cyclopropylacetylide can add to aldehydes, ketones, and electrophilic heterocycles to afford propargylic alcohols and related intermediates.

These versatile reaction profiles make C684376 a frequently chosen building block for the preparation of pharmaceuticals, agrochemicals, and functional materials.

Storage, Handling, and Safety

Storage: Store cyclopropyl (trimethylsilyl) acetylene in a tightly sealed container under an inert atmosphere (nitrogen or argon) in a cool, dry, well-ventilated location away from heat sources, ignition sources, and oxidizing agents. Refrigerated storage (2–8 °C) is recommended to maintain long-term stability. Keep away from moisture to prevent hydrolytic degradation of the TMS group.

Handling: Use appropriate personal protective equipment (PPE) including chemical-resistant gloves, safety goggles, and a lab coat. All manipulations should be performed in a well-ventilated fume hood. Avoid inhalation of vapors and contact with skin or eyes. Employ standard Schlenk or glovebox techniques when working with air- or moisture-sensitive quantities.

Disposal: Dispose of waste material in accordance with local, national, and institutional regulations for flammable organosilicon compounds. Do not pour down drains.

Note: Always consult the current Safety Data Sheet (SDS) for C684376 before use.

Ordering and Quality Information

Cyclopropyl (trimethylsilyl) acetylene is available from Aladdin Scientific under SKU C684376. When placing an order, researchers and procurement teams should note:

• Purity: Confirm the certificate of analysis (CoA) for lot-specific purity data prior to use in sensitive applications.
• Pack sizes: Contact Aladdin Scientific or consult the product page for available quantities and pricing.
• Lead time: Standard stock items typically ship promptly; custom or bulk quantities may require additional lead time.
• Documentation: SDS, CoA, and structural confirmation data are available upon request or via the Aladdin Scientific website.

For technical questions about this product, contact the Aladdin Scientific technical support team. For account, payment, or shipping inquiries, please refer to the Help and Customer Service section of the Aladdin Scientific website.

Frequently asked questions

What is cyclopropyl (trimethylsilyl) acetylene used for in organic synthesis?

Cyclopropyl (trimethylsilyl) acetylene serves as a versatile building block in organic synthesis. It is commonly used as a TMS-protected source of cyclopropylacetylene for Sonogashira cross-coupling reactions, nucleophilic addition to carbonyl compounds after metalation, and cycloaddition chemistry. The cyclopropyl group also introduces a conformationally restricted, bioisosteric motif valued in medicinal chemistry.

How do I remove the TMS protecting group from cyclopropyl (trimethylsilyl) acetylene?

The TMS group can be removed under mild conditions using a fluoride source such as tetrabutylammonium fluoride (TBAF) in THF, or using potassium carbonate (K₂CO₃) in methanol at room temperature. These conditions selectively cleave the Si–C bond to give free cyclopropylacetylene without affecting most other functional groups present in the molecule. The choice of deprotection method should be guided by the sensitivity of other functional groups in the substrate.

What are the recommended storage conditions for cyclopropyl (trimethylsilyl) acetylene (C684376)?

The compound should be stored under an inert atmosphere (nitrogen or argon) in a sealed container at 2–8 °C, away from moisture, heat, and ignition sources. Exposure to moisture can cause hydrolysis of the TMS group, reducing reagent quality over time. Always check the current SDS and CoA for lot-specific storage guidance.

Is cyclopropyl (trimethylsilyl) acetylene suitable for Sonogashira coupling reactions?

Yes, after deprotection of the TMS group to reveal the free terminal alkyne, cyclopropylacetylene is a well-suited partner for palladium/copper-catalyzed Sonogashira coupling with aryl and vinyl halides. The reaction allows efficient incorporation of the cyclopropyl-alkyne unit into diverse molecular frameworks. Some protocols may also employ the TMS-alkyne directly under proto-desilylation conditions in situ.

What safety precautions should be taken when handling this compound?

Researchers should wear chemical-resistant gloves, safety goggles, and a lab coat, and conduct all operations in a well-ventilated fume hood. The compound is an organosilicon liquid that may be flammable; keep it away from open flames and heat sources. Avoid inhalation of vapors and contact with skin or eyes. Refer to the current Safety Data Sheet (SDS) for comprehensive hazard and first-aid information specific to lot C684376.

References

1. General reference: Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic Synthesis, 4th ed.; Wiley: Hoboken, NJ, 2007. (For TMS deprotection strategies of alkynes.)
2. General reference: Sonogashira, K. Development of Pd-Cu catalyzed cross-coupling of terminal acetylenes with sp2-carbon halides. Journal of Organometallic Chemistry, 2002, 653, 46–49. doi:10.1016/S0022-328X(02)01158-0
3. Aladdin Scientific Product Page: Cyclopropyl (trimethylsilyl) acetylene, SKU C684376. Aladdin Scientific, Shanghai.

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